CPAP devices, originally used for treating sleep apnea, are now also used to treat respiratory distress. In this latter application, medication may be fed into the airflow using a nebulizer. A nebulizer is a device having a reservoir of liquid medicament and which uses a source of pressurized gas, such as oxygen or compressed air, to disperse the medicament into aerosol droplets which can be inhaled by a patient. Thus, when used in combination with a CPAP apparatus, the aerosol droplets generated by the nebulizer can be combined with the breathable fluid delivered to the patient via the CPAP apparatus. The CPAP apparatus and the nebulizer each require a source of pressurized breathable fluid in order to operate. Thus, conventionally, two distinct sources of pressurized breathable fluid have been required when a nebulizer is to be used in conjunction with a CPAP apparatus. U.S. Patent Application Publication No. 2003/0217749 discloses an apparatus for delivering a breathable gas together with a nebulised medicament to a patient using a single gas cylinder, but requires that two separate lines be connected to the gas cylinder.